Such a cable is intended in particular for long distance data transmission.
Document EP-A-0 696 750 discloses a cable of that type, in which the optical fibers, whether independent from one another or assembled together in at least one ribbon, are contained inside a protective tube of plastic together with a filler material for filling the tube. The reinforcing elements of the tube are made of a plastics material that is reinforced by reinforcing fiber and known as FRP material, and they are cabled on the protective tube by being assembled to one another. The outer sheath of the tube is extruded over the reinforcing elements once they are in place.
To manufacture such a cable, the optical core defined by the protective tube containing the optical fibers and the filler material is often made initially on a first manufacturing line, while the reinforcing elements are made and put into place around the optical core, with the outer sheath being simultaneously extruded thereabout, on a second line for cable manufacture proper. The differences between the materials of the protective tube and of the sheath in particular mean that stresses can be generated while the extruded sheath is cooling, which stresses are then transmitted to the protective tube and are liable to affect the fibers contained in said protective tube. As a result, the cable is made in two stages and manufacture is lengthy, thereby causing the cost of the cable to be relatively high.
An object of the present invention is to provide an optical fiber cable of a structure that avoids those problems so as to enable it to be made in a single stage.
The invention provides a reinforced optical fiber cable of unitube structure comprising a protective tube for protecting optical fibers and reinforcing elements around said protective tube together with an outer sheath, wherein said protective tube is of corrugated tubular structure.
Additionally and advantageously:
the corrugated tubular structure is constituted by a transversely corrugated metal strip that is deformed longitudinally into a tube, or is made of a plastics material and is extruded;
the reinforcing elements include a reinforcing layer between said corrugated tubular structure and said outer sheath and/or cords that are strong in traction embedded in the outer sheath parallel to the axis of the cable, being disposed diametrally opposite one another in pairs and close to a diametral plane of said cable.